My engine has always run rich, even putting my scan tool on it I can fin nothing which is outside of the parameters. At the end of this season I plan to get into the injectors. Start off with doing a balance test and if the injectors are the issue either rebuild or have them rebuilt/replaced. Has anyone ever tried rebuilding or would this be a bit to much for the back yard mechanic? With the cost of new ones at the $160 to $200 each area, and rebuilds in the $100, looking for some ideas. I find some GMC injectors but can not cross to the Merc number

Probably going to replace the MAP and air temp sensor just for giggles.

Edit: forgot 502 Mag MPI

Vst used 36 lb injectors cool fuel 42 lb I believe. I had 8 custom built larger cc injectors when I bumped up my hp in my 94 454 mag vst I think for less than 540 shipped. I will have to look for company name. Bench testing usually 200 itself.

http://www.ebay.com/itm/8-Walker-500...r#ht_324wt_805


http://www.ebay.com/itm/MAR100-8-Set...ht_4445wt_1050

As an additional source to the above posted links, RC Injection in Torrance, CA has KEIHIN style replacements as well. I would not rebuild but rather flow check, clean and flow balance first.

Thanks guys for the info. The boat seams to run fine but every year my plugs are fairly fowled. Picked up the Rhinda scanner and may balance test will show something. Guess it would be better to replace then rebuild as you mentioned. The ebay items shows where one is for 7.4 and 502 isn't listed, and the other shows a 502 and 48 lb. Both show the same Merc part number.

Jegs has some 48lb injectors and if I have 48lb and not the 36lb (don't know), Service manual 16 indicates fuel pressure should be 34-38 psi.
http://www.jegs.com/p/Accel/Accel-Pe...183&Ntt=749691

Could it be you could have higher pressure injectors (48) even though you may only put out 38?

Keep in mind if you change injectors (size) and keep the fuel pressure the same (I prefer factory specs), you will create a tune issue. In other words, assume you have a 42 lb injector and replace with a 36 lb injector you will run leaner. Conversely swapping to a 48 lb injector you would run richer. All this is assuming you have not touched the ECM fuel table.

You may be compounding your issue by swapping injectors. Clean and flow test the stock injectors and if they all come back to spec I'd run them and live with wet plugs since you stated the boat seems to run fine.

I also prefer factory, so guess I wasn't very clear with what I'm trying to figure out. The ebay links both indicate they are the correct Merc part numbers, but appear to be different. If I knew what pound injector is installed then I would know have the info needed to decide. Not knowing what is required is the cause for my questions. Fun Times on iboats mentioned yesterday about ultrasonic cleaning of the injectors and that may be the way to start, Get them cleaned and checked which will then tell me if I need any of them replaced. If they are 30, 36 or 48 would be good to know, then I could just shop of that instead of the Merc part number.

The boat does run fine, but I am starting to loose a bit of top end which is also usually what happened around this time. It will last the season and at the end I pull the plugs and they need a good cleaning. Two years ago I let it go for a year and then my knock sensor engaged and retarded timing. Cleaned the plugs and she was back up and going.

You may be down on power for several compounded reasons. The injectors may not be flowing correctly which can cause a lean situation, which in turn can cause detonation, which will cause knock retard and further lose power. Like you mentioned, clean and flow test to get a good baseline. If the injectors are restored I'd run them.

will add also the ECM / PCM receives inputs from sensors along with its tune to produce the outputs how long the fuel injectors with stay open & close. Its called pulse width. Throw the biggest injectors at it with everything else being stock including the fuel pressure regulator - you will be going backwards instead of forward with your mods and running condition..

Appreciate all the input, between what I'm getting at OSO and iboats I'm getting a good understanding of what my path forward will be. Was provided some 2008 and 2012 links to some threads here on OSO which discussed the same issue further. Keep it coming, I'll figure this thing out

http://forums.iboats.com/forum/engin...epair-805225a1